got oval instead of circle cambam->linuxcnc

Hi

any suggestions to solve the problem shown in the screenshot ? linuxcnc does not follow the line of the circle, it generates a oval out of the circle.

you see the g-code for the circle between line 14 and 18.

linuxcnc 2.6.9
cambam plus 0.9

cambam settings (linuxCNC postproc.):
arc center incemental G91.1
arc center absolute G90.1
arc center mode standard
number format 0.0####
arrow to line tolerance 0.01

any ideas for config settings (.hal, .ini ) to check (cambam or linuxcnc) ?

tnx

if your getting an oval instead of a circle , then you have mechanical axis issues
if this is a stepper machine, they you could be missing steps
or possibly your running the axis at velocity that it cannot handle

could even be your power supply is struggling , but mechanical issues are the main problem,
post your complete gcode file as an attachment

i'll take a guess this is a gantry machine , and theirs mechanical flex in the gantry and flexing front to back

Machine flex is a common source.

Cutting a circle tests the rigidity through 360 degrees.

Think it's a settings issue. The plot would not follow mechanical problems.

Looks like the trajectory planner is responsible. I might be wrong, but if your acceleration setting is low, then this can happen. What happens if you lower the feed rate?

I would check your G64 settings.

If not setup by your CAM programs preamble, the default is plain G64 which means
keep up feed rate regardless of path deviation...

linuxcnc.org/docs/html/common/User_Conce...c:trajectory-control


Minor nit, the plot can follow mechanical problems in a servo system
(where the backplot data is the actual position, not the commanded position)

PCW wrote:

I would check your G64 settings.

Minor nit, the plot can follow mechanical problems in a servo system
(where the backplot data is the actual position, not the commanded position)

Thanks, right! So used to stepper systems.
But only for lost steps, right? Not flex.
Another reason to get position feedback on mine.
Cheers!

Thanks a lot, it was a wrong G64 setting, changed it from

G64 Blend Without Tolerance Mode

to

G64 P0.05 Blend With 0.05 (mm) Tolerance